Fossil Record of Stickleback Evolution

This video explores the evolution of a stickleback fish population over tens of thousands of years, based on fossil data.

These fossils come from a quarry site in Nevada that used to be a freshwater lake about 10 million years ago. By studying the fossils from different rock layers, scientists can follow the evolution of the lake’s stickleback population over time. The video shows that the lake was initially populated with stickleback fish with a reduced pelvis (no pelvic spines). The population then rapidly became dominated by stickleback fish with a complete pelvis (with pelvic spines), probably due to an "invasion" of the lake by fish with this new form. However, as the population evolved over time, fish with a reduced pelvis became more common again.

This clip is from a 2005 Holiday Lecture Series, Evolution: Constant Change and Common Threads.